CWS A or CWS B video ?

[Michael Moe 495]

Hi,

 

 

Is there any good video out there that demonstrate CWS in action ? 

 

Or maybe someone could help ?

 

Thanks

 

PS!

AOA does not seem to have it in there videos

 

(i do remember the russian crash in a Airbus that had the system but didnt educate the pilots or illustrated it in the cockpit )

[hopskip 253]

If you'v ever flown the tinmouse (with the sperry 77 autopilot), the only vertical mode is CWS and Altitude hold. So it can maintain an altitude, or an attitude, no FLCH, Vert-speed, or VNAV.

 

If you pull back on the yoke in CWS, the nose attitude will increase. If you return the yoke to neutral, the nose will maintain that attitude. There is no speed or stall protection and the climb rate will depend on altitude and speed. The deck angle will stay the same till changed (or till impossible in a stall).

[Meese 5]

To explain it very easily, it basically enables the 737 to fly like an Airbus.

 

I've asked a few flight crews about it, and almost everyone says it's rarely/never used amongst the pilots they know. This is at least pretty unanimous across Norway/Scandinavia, can't account for other parts of the world.

[hopskip 253]

To explain it very easily, it basically enables the 737 to fly like an Airbus.

Not really. CWS doesn't have any protections against speed decay, overspeed or stall. It just keeps the attitude in one place by adjusting the trim and aelerons to maintain the same attitude even as speed changes or turbulence is encountered.

 

I've asked a few flight crews about it, and almost everyone says it's rarely/never used amongst the pilots they know. This is at least pretty unanimous across Norway/Scandinavia, can't account for other parts of the world.

This bit's pretty true though. I'v seen some airline SOP's actually do not allow it's use, and it'd be very unlikely to be used in an NG anyway. However, as it's an integral part of the early 737-200 autopilot, it's included probably for cockpit commonality.

 

Also it's the mode the aircraft will revert to if:

1: An autopilot mode (such as VNAV) is deselected without being replaced by anything. (ie VNAV button pressed when Autopilot CMD is already in VNAV mode).

2: If the yoke is moved significantly when autopilot is engaged.

and of course 3: if one of the CWS buttons is pressed.

[Spin737 102]

I've used it for weather deviations. Alt hold and CWS ROLL works fine.

 

Some like to use it for climbing at a constant deck angle.

 

Also, it's good for turbulence encounters.

[hopskip 253]

HDG mode is less lazy and less likely to 'skim the side' of cloud... but using it for unusual things like VFR tracking coastal contour flying while maintaining an altitude, or a level segment of a VFR approach might work.

 

The constant deck angle climb was used in the 737-200 (Sperry), I don't much like it because deck angle doesn't correlate to any speed or rate of climb, and without pushing forward to lower climb rate before levelling off into Alt hold, the aircraft might well punch through altitude and then pitch over to decend back to the Alt hold altitude.

 

Turbulence with CWS (in climb or decent) again looses all it's protections but is less bumpy, because the aircraft isn't trying to pitch up/down to maintain a vertical rate or speed (or altitude even).

Suggest not using CWS in tightly packed RVSM when you should be level .

[Spin737 102]

HDG mode is less lazy and less likely to 'skim the side' of cloud

That sounds like a personal preference. I don't know what could be less lazy that spinning the HDG bug. Sometimes I do CWS, sometimes I do HDG SEL, depending on the situation.

without pushing forward to lower climb rate before levelling off into Alt hold, the aircraft might well punch through altitude and then pitch over to decend back to the Alt hold altitude.

CWS will do quite nicely leveling off with ALT ACQ and then ALT HOLD. In that regard, it's no different than LVL CHG.

Suggest not using CWS in tightly packed RVSM when you should be level .

RVSM is a few down on the list of priorities when in a strong mountain wave or severe turbulence. Follow the correct AFM and ATC procedures, and you're all set. That does include using CWS.

[tcas_climb 45]

Yep the severe turbulence checklist in the qrh recommends switching to CWS.